The invention relates to reducing hair growth in mammals, particularly for cosmetic purposes.
A main function of mammalian hair is to provide environmental protection. However, that function has largely been lost in humans, in whom hair is kept or removed from various parts of the body essentially for cosmetic reasons. For example, it is generally preferred to have hair on the scalp but not on the face.
Various procedures have been employed to remove unwanted hair, including shaving, electrolysis, depilatory creams or lotions, waxing, plucking, and therapeutic antiandrogens. These conventional procedures generally have drawbacks associated with them. Shaving, for instance, can cause nicks and cuts, and can leave a perception of an increase in the rate of hair regrowth. Shaving also can leave an undesirable stubble. Electrolysis, on the other hand, can keep a treated area free of hair for prolonged periods of time, but can be expensive, painful, and sometimes leaves scarring. Depilatory creams, though very effective, typically are not recommended for frequent use due to their high irritancy potential. Waxing and plucking can cause pain, discomfort, and poor removal of short hair. Finally, antiandrogens—which have been used to treat female hirsutism—can have unwanted side effects.
It has previously been disclosed that the rate and character of hair growth can be altered by applying to the skin inhibitors of certain enzymes. These inhibitors include inhibitors of 5-alpha reductase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, gamma-glutamyl transpeptidase, and transglutaminase. See, for example, Breuer et al., U.S. Pat. No. 4,885,289; Shander, U.S. Pat. No. 4,720,489; Ahluwalia, U.S. Pat. No. 5,095,007; Ahluwalia et al., U.S. Pat. No. 5,096,911; and Shander et al., U.S. Pat. No. 5,132,293.
Telomerase is an enzyme that is responsible for catalyzing the addition of simple hexameric nucleotide sequences on the ends of linear chromosomal DNA. The ends including these sequences generally are known as “telomeric DNA.” Telomeric DNA typically is up to 200 base pairs long in humans. The maintenance of telomeric DNA by telomerase protects the cell from exonucleocytic degradation and subsequent cell senescence. With each cell replication telomeric DNA, which consists not of blunt-ended double stranded DNA but rather of a 3′ single stranded G-rich protruding overhang, shortens and, once reaching a critical threshold, triggers the cell to senesce as a sort of checkpoint control. It has been postulated that this mechanism may represent a biological clock controlling the lifespan of the cell. To compensate for the loss of telomeric DNA during cell replication, cells express the enzyme telomerase, a ribonucleoprotein, which includes an RNA component that serves as a template for the synthesis of telomeric DNA. Certain cell types express high levels of telomerase. These include some tumor cells, cells of renewal tissues (e.g., skin, intestine, blood), and some immortalized cells with high proliferative capacity. Investigators have shown that telomerase is present in blood progenitor cells and activated lymphocytes, epidermis and intestine. Recent findings have shown that peripheral blood lymphocytes are “telomerase competent” such that if they are not dividing or quiescent they are telomerase negative and, when they are mitogenically activated and become proliferative, they are telomerase positive. Quiescent cells are always telomerase negative and cell proliferation is a prerequisite for telomerase activation in telomerase competent cells. It is possible that high telomerase levels reflect either a fraction of proliferating cells or markedly elevated telomerase activity in the individual cells.